Intermittent Fasting in Youth: A Scoping Review

Intermittent fasting (IF) focuses on the timing of eating rather than diet quality or energy intake, with evidence supporting its effects on weight loss and cardiometabolic outcomes in adults. However, there is limited evidence for its efficacy in adolescents and emerging adults. To address this, a scoping review examined IF regimens in individuals aged 10 to 25, focusing on methodology, intervention parameters, outcomes, adherence, feasibility, and efficacy. The review included 39 studies with 731 participants aged 15 to 25. Methodologies varied, with 18 studies on time-restricted eating and others requiring caloric restriction. Primary outcomes included cardiometabolic risk factors (11/29), body composition (9/29), anthropometric measurements (8/29), and feasibility (2/29). Most studies reported significant weight loss. This review underscores IF's potential in treating obesity in this age group but highlights the need for rigorous studies with standardized frameworks for feasibility to ensure comparability and determine IF’s practicality in this age group.

The focus of the review was to investigate IF interventions that included adolescent and emerging adults.To ensure that a wide range of relevant studies was captured, the following two-part research question was crafted to guide the search: In IF interventions that include adolescents and emerging adults: 1) What were the intervention parameters, adherence monitoring approaches and delity measures employed and primary and secondary outcomes captured, and 2) What is the reported feasibility and e cacy?
A structured search was applied utilizing the PubMed bibliographic database.The rst author (JAB) created the initial PubMed search strategy using a combination of Medical Subject Headings (MeSH) and keywords for intermittent fasting, health effects, and youth.The search was restricted to studies published since 2000, on humans, who are adolescents or young adults, and written in English.Intermittent fasting included time-restricted eating, intermittent energy restriction, and alternate day fasting interventions.Team members (JAB, SJS, and APV) reviewed the strategy and preliminary results to modify and improve the search strategy.With the team's approval, JAB customized the search using controlled vocabulary and keywords in the database listed above.The search strategy included the following terms: intermittent fasting OR time restricted eating OR time restricted feeding OR alternate day fasting OR intermittent energy restriction OR meal timing OR eating window AND weight OR metabolism OR metabolic OR body composition OR aging OR in ammation OR in ammatory OR oxidative stress AND youth OR young adult OR adolescent.All resulting citations were exported into a Mendeley library, and duplicates were removed.No additional efforts were conducted to seek out grey literature, including other study registries, websites, or conference proceedings.On March 31, 2024, the search was repeated in the bibliographic database to identify any more recent studies.

Study Selection.
Titles and abstracts were rst screened, and then eligible full-text articles were screened by one author (JAB) (title abstracts: n = 240, full-text n = 91).For the initial screening of abstracts, the inclusion criteria were as follows: (1) articles are in English; (2) included participants with age equal to or less than 25 years old; (3) report of a primary or second outcome that relates to a change in weight (body mass index (BMI), BMI z-score, weight in excess of the 95th percentile[%BMIp95], percent weight change), a change in metabolic markers (body composition, glycemic biomarkers, or lipid pro les), or a change in biological aging markers (in ammatory markers and oxidative stress).There was only one exclusion criterion.Studies on Ramadan IF were excluded due to its unique cultural and ceremonial context, which entails signi cant alterations in eating habits, sleep cycles, and often leads to increased consumption of high-sugar and high-fat foods, rendering its effects incomparable to other forms of health-promoting fasting [15].No exclusion criteria were applied to sample size or location.During subsequent full-text screening, the independent reviewers ensured the following criteria were met for all retrieved studies: (1) publication included full text and (2) publications were peer-reviewed.Ineligible reports included dissertations, conference abstracts and proceedings, unpublished protocols, and commentaries or opinion pieces.

Data Charting.
Before data charting, the authors discussed the various variables and reached agreement in terms of which variables were extracted based on the scope of the review.One reviewer (JAB) developed a data-charting form to determine which variables to extract and charted the data.Then, two reviewers discussed the results, and continuously updated the data-charting form.The data extracted included sample descriptions, methodology, outcome measures, assessments, and results of interventional studies.Next, one extractor reviewed all the articles and formed the table (JAB).An additional team member double-checked the extracted data and helped revise the table (APV).Data tables facilitated analysis.Participant characteristics across trial studies, interventions, measures, and results are summarized in Tables 1 and 2.

Ethical Considerations. Ethical approval
was not sought for this review as it relies on already published work.Additionally, this review was not registered in PROSPERO, the international database for systematic reviews in health and social care, due to the fact that scoping reviews do not ful ll the registration requirements (https://www.crd.york.ac.uk/prospero/#aboutpage).

Analytic Analysis
For each interventional study on the health effects of IF, the following data were abstracted: number of participants, ages of participants, study design, intermittent fasting regimen, additional intervention components, adherence monitoring method, feasibility assessment, primary and secondary outcome measures.The other included studies were analyzed conceptually, without charting of speci c data.

Study Selection.
Upon removal of duplicates, 237 titles and abstracts were screened for eligibility.A total of 91 underwent full-text review.Of those, 39 studies met the prespeci ed inclusion criteria.A PRISMA ow diagram detailing the database searches, the number of abstracts screened, and the full texts retrieved is illustrated in Figure 1.The study designs and methodologies of the included studies are cataloged in Figure 2. Of these studies, twenty-nine were interventional studies that focused on the e cacy of IF on weight, metabolism, and/or biological aging markers.Table 1 summarizes the key characteristics of the 29 interventional studies that included e cacy data, emphasizing intervention components, execution, feasibility measures, adherence monitoring, and primary and secondary outcomes.The remaining ten studies were observational studies focusing on evaluating the effects, acceptability, and implications of timing of eating within the context of weight management interventions, cardiometabolic risk factors, and eating behaviors in adolescents and young adults, without involving the experimental manipulation of timing of eating.

Participants.
Studies predominantly focused on adolescents and young adults, with mean ages between 15 to 25 years old [31,32,.Some included a majority of female participants (e.g., 64% in Vidmar et al. 2021) [31], while others only included male participants (e.g., 100% males in McAllister et al. 2020 and Harder-Lauridsen et al. 2017) [114,124].A few studies reported an even sex distribution [116].Participants' baseline weight status also varied widely, from those with a median or mean weight indicating overweight or obesity (e.g., median weight=101.4 kg in Vidmar et al. 2021) [31] to those with participants in the normal weight range (e.g., mean BMI = 22.7 kg/m² in Park et al. 2021) [112].

Study Design Characteristics.
Thirty-nine studies were included in this review.Ten studies did not involve interventional design, but rather examined the relationships between meal timing and weight management outcomes, cardiometabolic risk factors, and eating behaviors in adolescent and emerging adults [90][91][92][93][94][95][96][97][98]102,105].Twentynine were interventional studies that focused on e cacy or effectiveness of IF interventions on weight, metabolism, and biological aging markers, as summarized in Table 1 [31,32,.The primary outcomes varied, but primarily involved assessing the e cacy of various intermittent fasting interventions on body weight, body composition, cardiometabolic health markers, energy balance, and speci c physiological responses such as glycemic control and muscle damage indicators.Secondary outcomes were also diverse and included assessments of dietary intake quality, physical activity, sleep patterns, eating behaviors, quality of life, glycemic control, blood biomarkers, microbial diversity, muscular performance, hunger, craving, mood, cognitive function, appetite, and energy intake responses.Most interventional studies involved interventions with short duration, spanning 4 to 12 weeks, which limits conclusions about long-term e cacy and safety.Among these studies, twenty-one were RCTs [31,107,[109][110][111][113][114][115][116]120,121,123,124,126], ve were single-arm trials [32,108,112,122,125], and one was two-arm randomized trial [114].Eighteen studies utilized an 8-hour time-restricted eating window [31,95,107,108,111,112,114,115,119,[121][122][123]126], and two tested other forms of IF, including Alternate-Day Calorie Restriction [124] and Protein-Sparing Modi ed Fast [125].Other studies investigated different TRE windows or other IF protocols.and signi cantly reduced calories on 2 days of the week [116].Only one study conducted a comparative analysis between early and late TRE, providing unique insights into how the timing of eating windows within IF regimens can affect metabolic health, weight loss, and potentially other well-being markers [113].The caloric requirements varied across studies, with some implementing isocaloric conditions (maintaining the same caloric intake) [107,114], energy restriction (e.g., 25% calorie de cit, very low-calorie diets) [120], and intermittent fasting days such as alternate-day fasting (ADF) [32] and intermittent energy restriction (IER) [120].Speci c interventions like the protein-sparing modi ed fast (PSMF) had de ned caloric intake ranges (1200-1800 calories with low carbohydrate and high protein) [125].

Catalog of Feasibility Measures and Adherence Monitoring
To evaluate the acceptability and feasibility of healthcare interventions, a generic, theoretically grounded questionnaire was previously developed around the constructs of the Theoretical Framework of Acceptability (TFA) [133].This tool was designed to measure seven speci c elements related to feasibility: affective attitude, burden, ethicality, intervention coherence, opportunity costs, perceived effectiveness, and self-e cacy.This versatile questionnaire can be customized to analyze the acceptability of various healthcare interventions across diverse settings.Studies were evaluated on whether they measure acceptability and feasibility consistent with TFA.Table 2 presents an overview of the interventional studies, cataloged by the results reported.There was great heterogeneity in how feasibility was de ned across various study designs.None of the studies utilized the seven TFA components.A few of the individual components of the framework were captured: 7/29 affective attitude, 4/29 burden, 0/29 ethicality, 0/29 intervention coherence, 0/29 opportunity costs, 1/29 perceived effectiveness, and 0/29 self-e cacy.

Summary of Clinical Trials Body Weight
There was a variety of weight status and body composition measures utilized across reports making comparison of the effect of IF on body weight challenging.Most studies highlighted signi cant weight loss among participants adhering to IF protocols, though with varying degrees of weight reduction across studies and samples [31,107,108,[112][113][114][115].Vidmar et al. (2021) examined the e cacy of late TRE in adolescents with obesity.All groups experienced weight loss, with 31% of the participants of the TRE plus continuous glucose monitoring (CGM) group, 26% of the TRE with blinded CGM, and 13% of the control group [31].Hegedus et al. (2023) reported a signi cant decrease BMI at the 95 th percentile (%BMI p95 ) at week 12, with a 46% reduction observed in the late TRE (lTRE) group compared to 21% in the control group with an extended eating window [107].Zhang et al. (2022) observed decreases in weight and BMI in both early and late TRE groups compared to controls [113].
In Moro et al. (2020) study, the TRE group experienced a 2% weight change from baseline, while this was not the case for participants assigned to the control group [115].Park et al. (2021) documented signi cant weight loss among female participants, while no signi cant weight loss was observed among male participants [112].In contrast, research examining the combination of TRE with resistance training (RT) offers a different perspective [109,110].Tinsley et al. (2019) investigated the effects of an 8-hour TRE combined with β-hydroxy β-methylbutyrate (HMB) supplementation and RT in active females, only to nd an increase in body weight across all groups [110].Similarly, a study by Tinsley et al. (2017) on a 4-hour TRE regimen coupled with RT in men reported no signi cant change in body weight [109], indicating that the e cacy of TRE on weight loss might be in uenced by factors such as biological sex, baseline weight, and exercise regimens.

Cardiometabolic Risk Factors
Several studies reported improvements in markers of glucose metabolism [107,112,113].For instance, Hegedus et al. (2023) found reductions in hemoglobin A1c (HbA1c) and alterations in C-peptide levels in late TRE groups [107].Kim & Song (2023) observed reductions in fasting blood glucose and improvements in HOMA-IR, indicating better glucose regulation and insulin sensitivity [122].Zhang et al. (2022) highlighted a decrease in insulin resistance [113].One study also reported reductions in systolic and diastolic blood pressure [114].Conversely, two studies [32,109] observed no metabolic changes compared to baseline.Another study reported signi cant reductions in fasting insulin, acyl ghrelin, and leptin concentrations during energy deprivation compared to energy balance.Postprandial hormone responses, including insulin, GLP-1, and PP, were elevated after energy deprivation, while acyl ghrelin was suppressed, indicating that altered sensitivity to appetite-mediating hormones may contribute to the adaptive response to negative energy balance [105].Zhang et al. (2022) noted decreases in body mass and fat mass (FM) in participants adhering to TRE, while preserving lean mass [113,114].Additionally, IF was associated with decreased liver enzymes aspartate aminotransferase (AST) and alanine transaminase (ALT) in two studies [107,111].McAllister et al. (2020) reported increases in high-density lipoprotein (HDL) and variations in low-density lipoprotein (LDL) and total cholesterol depending on the type of TRE (ad libitum vs. isocaloric) [114].Zeb et al. (2020) found decreased total cholesterol (TC) and triglycerides (TAG), and an increase in HDL post-TRE [111].However, divergent effects on lipid pro les were observed as well, with increases in HDL [111,114] as well as in LDL [112,113].

Biological Aging Markers
Only a few studies measured markers associated with biological aging [111,[113][114][115]. McAllister et al. (2020) and Moro et al. (2020) both reported an increase in adiponectin levels in participants following an 8-hour TRE regimen, whether combined with an ad libitum diet or an isocaloric diet.Elevated adiponectin levels are inversely associated with obesity and oxidative stress and correspond to improved metabolism and resting energy expenditure [114,115].Additionally, Moro et al. (2020) observed a signi cant decrease in the neutrophil-to-lymphocyte ratio, an in ammatory marker, within the TRE groups compared to controls, indicating reduced in ammation [115].Zeb et al. (2020) observed reductions in serum IL-1B and TNF-a levels post-TRE, though these changes were not statistically signi cant, suggesting a potential trend towards reduced in ammation that warrants further investigation [111].Zhang et al. (2022) reported that superoxide dismutase (SOD), a crucial antioxidant defense in nearly all living cells exposed to oxygen, signi cantly increased in participants who engaged in early TRE compared to those in late TRE and control groups [113].

Summary of Observational Studies
Observational studies varied in their focus.Some addressed parental interest in time-restricted eating (TRE), while others looked into nutritional adequacy, concerns, and the e cacy of TRE [90][91][92][93][94]96]. Tucker et al. (2022) found that two-thirds of parents with children in pediatric weight management programs showed interest in time-limited eating (TLE) for ≤12 hours per day, with interest waning for stricter limits of ≤10 or ≤8 hours [90].Lister et al. (2020) challenged the notion that continuous energy restriction (CER) is the sole method for weight management in metabolically unhealthy adolescents, proposing intermittent energy restriction (IER) as a viable alternative in tertiary settings [91].Similarly, Lister (2017) emphasized the need for careful consideration of nutritional adequacy in energy-restricted diets, highlighting that various eating patterns can achieve both nutritional adequacy and energy restriction, which is crucial when prescribing diet interventions for adolescent weight loss [92].Nevertheless, skipping breakfast was associated with increased cardiometabolic risk factors in adolescence, as observed is a cross-sectional survey study by de Souza et al. (2021) [93].One study reported that diets low in carbohydrates and those involving intermittent fasting were linked to increased disordered eating behaviors, including binge eating and food cravings.These ndings suggest that such restrictive diets may heighten cognitive restraint, leading to an upsurge in food cravings.However, this study's reliance on a cross-sectional design and a web-recruited university sample, predominantly female, introduces potential biases [102].
One review study evaluated the impact of the timing and composition of food intake, physical activity, sedentary time, and sleep on health outcomes, suggesting that these factors independently predict health trajectories and disease risks.This underscores the need for a unifying framework that integrates time-based recommendations into current health guidelines for children and adolescents [94].However, the practical implications of IER, such as the risk of fostering restricted eating patterns and inhibiting growth in adolescent girls on a 600-700 kcal diet, raise concerns.Vanderwall et al. (2020) pointed out that physical activity, an essential strategy for preventing obesity and metabolic syndrome, was not adequately measured in some studies, despite its likely contributory impact.These ndings collectively highlight the potential bene ts and challenges of dietary interventions like TLE, CER, and IER, emphasizing the importance of ensuring nutritional adequacy and integrating physical activity for effective adolescent weight management [96].
Observational research examining the relationships between the timing of eating, weight management outcomes, and cardiometabolic risk factors suggests there is no meaningful impact on body composition.However, there may be bene ts to cardiometabolic health from adopting earlier and shorter eating windows [97,98,132].These ndings are consistent with studies in adults indicating that aligning meal consumption with circadian rhythms can enhance metabolic outcomes [134,135].One possible explanation for the disparate ndings across clinical trials and observational studies is that existing observational studies have failed to consider how eating timing interacts with eating window duration to in uence health.Studies in adults have reported that eating late in the day, even with shorter eating window, can worsen postprandial glucose levels and b-cell responsiveness or confers no health bene t [136].More studies are needed to better characterize the joint in uence of eating timing, eating frequency, and daily eating duration on health outcomes.

Discussion
This scoping review catalogs published studies of intermittent fasting interventions in young people up to age 25.The review included 39 studies and revealed that there is a great heterogeneity in study design, methodology, feasibility measures, adherence monitoring, and intervention components across studies of IF in adolescents and young adults.The diversity of methodologies and outcomes makes it challenging to summarize overall e cacy of IF.
While IF interventions have the potential to be a feasible and acceptable treatment approach for adolescents and young adults, the current results highlight the need for rigorous studies to investigate feasibility of novel interventions, such as IF, utilizing standardized theoretical frameworks for acceptability to allow for comparability across studies and cohorts.As highlighted in the results; the majority of the studies included captured one to three of the seven recommended components associated with the acceptability framework however none utilized all seven components in their entirety.In addition, the majority captured this data via self-report and open-ended questionnaire with very little qualitative data to drive conclusions regarding feasibility and acceptability of IF interventions in this age group.Furthermore, the intervention components investigated varied signi cantly.This was not only found among what form of IF intervention was studied but what additional components of the intervention were included.It very well may be that IF based interventions can act as a synergistic intervention to other multi-component health and behavior approaches but the studies cannot truly be compared for e cacy when the interventions are not similar in their components.Each IF approach may be uniquely suited to a speci c individual's preferences, life stage, and resources.Thus, large, well-designed feasibility and e cacy trial should be performed for each IF approach compared to a control arm that is standardized across study designs to allow for comparability.In pediatric practice, investigators may consider utilizing a multidisciplinary, family-based intervention model given that is the most utilized health and behavioral lifestyle intervention implemented in this age group.Time restricted approaches were the most commonly studied form of IF included in this review.Even among TRE interventions there remains much opportunity for diversity in the approach which effects outcomes.As show in the results, the timing of the eating window varied by study design with the majority allow for a participant identi ed eating window followed by an afternoon/evening window.This variation in study design emphasizes an important mechanistic component of IF research across all age groups regarding the underlying mechanism that results in improvement in weight and cardiometabolic risk.There remains debate as to which eating window is most preferred by participant as well as which eating window results in the greatest improvement in weight and cardiometabolic outcomes when adhered to well.Further research is needed to understand both of these questions and allow for the mechanistic discover underling IF interventions as well as the pragmatic approach to how to actually disseminate this type intervention in a real-life setting to optimize engagement and thus sustained e cacy [97].
Given that adherence to treatment recommendations is the strongest predictor of weight loss; rigorous adherence monitoring is needed in the assessment of novel intervention approaches to truly understand e cacy [5][6][7][8].There was great variety in the methods utilized to capture adherence to the intervention across studies limiting comparability as well as ability to assess how the dosage of the intervention received effected the primary outcome of interest.To move the eld of IF interventions forward, it is essential to understand how best to implement and disseminate IF interventions in pediatric cohorts.Thus, not only is adherence monitoring required but also the personnel required for adherence monitoring, delity training, and prevention of intervention drift to ensure sustained engagement overtime.
Despite the limitations described above, the preliminary e cacy discussed in the reviewed articles exploring the effects of IF on weight loss and cardiometabolic outcomes is consistent with ndings reported in adult cohorts [13,14,31].Despite the diversity in participant demographics and IF strategies-including varying time-restricted eating windows and intermittent energy restriction combined with exercise or supplementation-the research indicates IF, especially TRE, can signi cantly improve weight loss, body composition, and metabolic health, with potential bene ts against metabolic syndrome and type 2 diabetes in adolescent and emerging adult cohorts.However, due to heterogeneity in methodology and quality of the evidence it is challenging to compare the e cacy across studies.Moreover, in adults IF interventions have been shown to have positive effects across other clinical outcomes such as aging, oxidative stress, and in ammation.The current results show the gap in mechanistic data that is available on how IF interventions effect other complex clinical outcomes that may have signi cant relevance to the long-term bene ts of this novel approach [137,138].
Finally, this review draws attention to both the gaps in research regarding the use of IF in adolescents and emerging adults and the opportunities.Expanding diverse nutrition interventions that are developmentally appropriate, practical, and easy to implement across communities and age groups is essential.IF uniquely allows individuals to maintain control over their food choices within a speci ed eating window.This exibility in choosing foods, selecting an appropriate eating window, socializing during meals, and dining out without dietary restrictions distinguishes IF as a dietary strategy that fosters sustainable behavioral change for an age group in which autonomy is expanding [18,31].Given that adolescence is a period of growing independence, re ected in food choices and time management [139], further research is needed to understand adolescent and emerging adult eating patterns and frequencies and how those patterns may affect intervention implementation and dissemination.
The practical implications of the ndings from this scoping review on intermittent fasting among youth are signi cant for parents, educators, and healthcare providers.These stakeholders play a crucial role in shaping the health behaviors of young individuals.By understanding the potential bene ts and considerations of IF based on current research, they can better guide and support youth in making informed decisions about their dietary practices.The collective insight from the current review calls for a re ned understanding of how IF interventions are designed and implemented in this age group to best accurately capture feasibility and e cacy.

Strengths and Limitations
To our knowledge, this is the rst review of IF evidence among adolescents and young adults.The summary of available studies' methodology, intervention parameters, outcomes selected, feasibility and e cacy ll an important gap in informing future research priorities.While comprehensive in its scope, the review also has several inherent limitations that could in uence the interpretation and applicability of its ndings.First, this review's ability to draw generalizable conclusions is challenged by the inherent heterogeneity in design, duration, sample size and characteristics, and methodologies.This variability hinders the broad picture interpretation of IF's e cacy.Particularly concerning is the lack of consistency is capturing intervention adherence.Dosage of the intervention is directly associated with e cacy and thus must be included to ensure e cacy accurately re ects the effect of the intervention.The short duration of many studies on IF involving adolescents and emerging adults, limits the understanding of IF's long-term effects on growth, development, and overall health in this demographic.Additionally, the potential for publication bias, where studies with positive or signi cant results are more likely to be published than those with negative or inconclusive ndings, could inadvertently skew the review's ndings in favor of IF.The exclusion of grey literature and non-English texts may further introduce bias, potentially overlooking relevant ndings not captured in the mainstream or English-speaking research community.Moreover, the review's approach did not extend to quantifying the quality of reporting or to an in-depth exploration of the methodological quality of the included studies, leaving a gap in our comprehension of the strength and reliability of the evidence base.Together, these limitations highlight critical areas for improvement in future research, underscoring the need for more rigorous, comprehensive, and long-duration studies to fully understand IF's impact on youth.

Conclusion
In conclusion, our scoping review of 39 studies on intermittent fasting among adolescents and emerging adults highlights signi cant variability in methodologies, intervention components, feasibility measures, and adherence monitoring, which complicates the assessment of study quality and comparability.This review underscores the need for rigorous studies using standardized theoretical frameworks for acceptability and feasibility to enable comparability across studies and cohorts.This is crucial to determine the practicality and sustainability of IF interventions in this age group.Further research, especially long-term studies, is essential to better understand IF's impact on youth, develop standardized methodologies, and ensure protocols that promote adherence and con rm clinical e cacy.No signi cant differences in weight were reported.
No signi cant differences were reported for glucose concentrations.
Signi cant trial effect for CHO oxidation, with higher rates in FED trials (P = 0.001).

N/A
[130] Not speci cally measured or reported.Not speci cally measured or reported.
No signi cant differences in Signi cant effect of the fasting group on N/A For instance, Zhang et al. 2022 compared early (7:00 a.m.-1:00 p.m.) and late (12:00 p.m. -6:00 p.m.) 6-hour TRE windows [113], and Bao et al. 2022 tested the e cacy of a 5.5-hour TRE window compared to an 11-hour eating control group [118].In total, eight studies involved multicomponent interventions combining TRE, continuous glucose monitoring (CGM), resistance training (RT), energy restriction, low carbohydrate and added sugar diets, brisk walking, high-intensity exercise, antioxidant supplementation, and protein-sparing modi ed fasts (PSMF).Keenan et al. 2022 compared continuous energy restriction with 5:2 intermittent fasting, where the IF group consumed normal calories for 5 days

Table 1 .
Overview of intermittent fasting studies among adolescents and young adults that included e cacy data cataloged by study characteristics, study design, and outcomes.

Table 2 .
Overview of intermittent fasting studies among adolescents and young adults that included e cacy data cataloged by results reported.
HOW: The perceived recovery scale (PRS), daily analyses of life demand for athletes (DALDA), and visual analogue scales (VAS)